In German Gebrauchsmuster (Utility Model) No. 72 41 371 there is disclosed a screw extrusion device which includes a measuring apparatus suitable for measuring the axial back-pressure exerted upon the plasticising screw. At the end of the plasticising screw which is subjected to an axial back-pressure, a disc-shaped deformation element or component is provided behind a back-pressure bearing, and a strain gauge in the form of semi-conductor expansion measuring strips is bonded or adhered to the deformation component. The expansion measuring strips are connected to a suitable measuring and indicating apparatus.
Additional component parts are required internally of the transmission for the mounting of the disc-shaped deformation component, thereby rendering the gear or back-pressure bearing considerably more expensive to produce.
Furthermore, it is not possible to provide corresponding, disc-shaped deformation components for both screws. This is because the space which such components would occupy behind the second shaft is required for the output shaft itself. An annular deformation component disposed behind the back-pressure bearing of the second screw shaft would be considerably more expensive than a conventional disc-shaped deformation component.